1. Field of the Invention
This invention relates generally to the welding of orthodontic articles and in particular, the method, apparatus and the orthodontic article itself. In particular, this invention relates to a method of laser welding the orthodontic article and the apparatus for accomplishing the method by an automated process.
2. Background
An orthodontic device known commonly as braces comprises two elements, namely, a bracket body and a pad. The elements are typically made separately and then permanently connected to one another for use. In some cases, the bracket body is tack welded to the pad, which is fabricated in strip form to facilities an automated permanent binding of the bracket body to the pad.
The pad is sized and shaped to conform to the teeth of the user and the surface contacting the teeth is generally concave. Adhesive is applied to the concave surface of the pad for facilitating a bond between the orthodontic device and the teeth of the user.
The bracket body provides the guiding structure for the arch wire and provides tie wings for manipulation for aligning and adjusting of the fit between the teeth and the brace. The arch wire goes around the braces and supports and aligns the teeth according to the expert manipulations of the dentist.
Typically, the bracket body is tack welded or otherwise only semi-permanently adhered to the pad. A gold braise or weld or similar treatment is then performed to connect the elements of the orthodontic device permanently. However, it is also known that gold braising requires high temperatures which may damage the braise or the elements of the orthodontic device and is not amendable to process automation.
Typical orthodontic devices have been made from materials such as ceramic (U.S. Pat. No. 5,205,734) or metal (U.S. Pat. No. 5,746,593). Some have even tried plastic with metal reinforcement (U.S. Pat. No. 5,692,898). Increasingly some metal material is used in at least part of the orthodontic device. More recently, Titanium is used as one of the elements of the orthodontic device. In fact, many new orthodontic devices are being made where Titanium forms at least a substantial part of the orthodontic device, see the disclosures of U.S. Pat. No. 5,746,593 and U.S. Pat. No. Re. 35,170. Very often some composition of Titanium and Nickel Titanium (Ni2Ti2) are now being used to form the entire bracket body and the pad.
Unfortunately, conventional methods and techniques for permanently connecting the pad and the bracket are simply ineffective on such Titanium based elements. Additionally, conventional methods of forming the permanent connection between the bracket body and pad are becoming less desirable as the standards for such orthodontic devices becomes more closely regulated. These regulations require that the seal between the pad and the bracket body be complete, in fact, certain state regulations require that the seal between the two elements be hermetic. Neither conventional welding nor gold braising is equipped to create such a seal between the elements. Moreover, neither braising nor conventional welding nor other known techniques can form a proper seal on Titanium based orthodontic products such as those described above.
Other known techniques such as microwelding as described in U.S. Pat. No. 4,249,060 for intra oral welding are similarly ineffective at creating the proper seal described above. Similar methods of making a bracket body of plastic with metal reinforcement (U.S. Pat. No. 5,692,898) are not relevant to the device, method and apparatus of the invention described herein.
In commercial applications, it is desirable to automate the manufacturing process to make the manufacture of such orthodontic devices cost effective. Typically, as illustrated in the drawing herein, the work piece, comprises the pad separated from and needing to be permanently attached to the bracket. The work pieces are provided in the form of strips of tack welded bracket bodies and pads. An automated process and apparatus must be created whereby the work pieces are fed through the joining apparatus to accomplish the permanent bonding. The needed apparatus for accomplishing such permanent bonding must be accurate as the work pieces are quite small and are numerous as well as intricate. Even minor damage or blemishes to the work piece would be sufficient to cause the work piece to be rejected. The rejection of a plurality of work pieces would be catastrophic to the manufacturer""s investment. Additionally, the method and apparatus must provide a high quality bond which is impervious to the caustic environment of the human mouth. And, of course, since the work piece is designed to fit within the human body there must be a high degree of quality assurance that each work piece is suited to its purpose.
What is needed is an orthodontic device that fulfills the above requirements made by a method and an apparatus that provide a sustainable return on the manufacturer""s investment. This is especially critical when the work piece provided is made from materials such as Titanium or Titanium based alloys. In the disclosed invention, a new, novel and non-obvious method and apparatus is used to create such an orthodontic device.
It is an object of this invention to provide a orthodontic device, which is laser welded so that the pad is permanently joined to the bracket body by laser welding the two together.
It is an additional object of this invention to provide a method for making such a laser welded device and additionally making a laser welded orthodontic device by an automated process.
It is an additional object of this invention to provide an apparatus for making the laser welded orthodontic device by the method of the invention and for making the laser welded orthodontic device by the automated method of the invention.
In accordance with the above objects and those that will be mentioned and will become apparent below, the orthodontic device in accordance with this invention comprises:
a pad;
a bracket body;
the bracket body being laser welded to the pad.
In an exemplary embodiment, both the pad and bracket body are made from Titanium. Also, in an exemplary embodiment the work piece forms a generally rectangular shape and the pad has one surface with a generally concave shape for the surface which contacts the teeth of the user.
In an exemplary embodiment of the method of the invention, the method of manufacturing which comprises the steps of:
providing a pad and a bracket body;
tack welding the pad and the bracket body together, and laser welding the pad to the bracket body for permanent connection.
In an exemplary embodiment, the method in accordance with the invention includes the step of spot welding at the contacting surfaces between the bracket body and the pad. In an exemplary embodiment, such spot welds are abundant and overlap each other at least partially, so that the perimeter around the work piece, between the bracket body and the pad, forms a seam weld and a seal. In fact, the seal is a hermetic seal between the bracket body and pad and around the perimeter of their joining.
An automated method of providing laser welded orthodontic articles comprises:
providing a strip of work pieces including a pad and a bracket body being tack welded together;
providing a laser member having at least one laser for laser welding together the work pieces;
laser welding at least one side of the work piece; and
rotating the laser member to weld a second side of the work piece and continuing rotation of the laser member until the entire perimeter formed by the contacting surfaces of the pad and bracket body are welded.
In another aspect of the invention, an apparatus for manufacturing the orthodontic article, comprises:
a laser welding member for creating a weld on all sides of the work piece;
a laser focusing member for focusing the laser into a single beam;
a laser alignment member for moving the laser welding member around the work piece, for facilitating creating a weld on all sides of the work piece; and
an indexer member for moving the work piece into position to be welded.
In an exemplary embodiment the laser welding member includes two laser focusing members spaced approximately 180xc2x0 apart. The opposed laser members are connected to an overhead rotatable platform, which, after welding, on two sides of the generally rectangular work piece are then rotated to weld the two remaining sides of the work piece.
As noted below in greater detail, the laser focusing members must operate so as not to cause the laser beam to strike either the work piece being welded or an adjacent work piece. In other words, the laser beam must be positioned so as to strike only the desired location. In order to maintain proper yield rates and the desired quality assurance, only that area designated for welding can be struck with a laser beam.
Additionally, in an automated exemplary embodiment, the apparatus in accordance with the invention includes an indexer which includes a mechanism for timing the movement of the next work piece ready for laser welding after the first work piece has been completed.
A computerized exemplary embodiment is also included as part of the invention herein. In this embodiment, the apparatus includes a laser alignment member operated by a computer and computer software. The laser alignment member adjusts and aligns the laser member so that the laser spot welds are positioned precisely in the desired location regardless of the specific configuration of the work piece. It will be appreciated that the work piece may vary in size and shape and the apparatus must be able to easily adapt to such dimensional changes. By providing appropriate software, the dimensional limits of the work piece may be entered into the computer and the computer will make the appropriate adjustments so that the laser alignment member functions as described above. Also, the indexer apparatus and laser focusing members are also controlled by the computer and its software as well as the timing described above.
It is an advantage of this invention to provide a laser welded orthodontic article which includes a hermetic seal around the perimeter of the adjoining surfaces of the pad and the bracket body.
It is an additional advantage of this invention to provide a method of laser welding a series of work pieces to provide economic and well constructed such orthodontic articles, which meet international standards.
It is an additional advantage of this invention to provide an apparatus, which facilitates automated manufacture of orthodontic articles by laser welding.